On the anniversary of the attacks by right-wing extremist Anders Behring Breivik, several commemorative events were planned.
The events were due to be attended by survivors and bereaved families as well as Prime Minister Erna Solberg and representatives of the royal family, among others.
The names of all 77 victims would be read out several times during the day.
At a national commemoration in the evening, King Harald V plans to give an address.
He then drove to the Island of Utoya, where he posed as a policeman and opened fire on participants at the annual summer camp of the youth organisation of the Labour Party.
A total of 69 people, mostly teenagers and young adults were killed on the Island.
Breivik cited right-wing extremist and Islamophobic motives for his actions and was sentenced in 2012 to the maximum sentence of 21 years’ detention with a minimum term of 10 years.